1. Field of the Invention
The present invention relates to a wet-formed composite. Specifically, the present invention relates to a wet-formed absorbent composite comprising an absorbent material and fibers.
2. Description of the Related Art
Absorbent composites suitable for use in absorbent products such as diapers, feminine care products, adult incontinence products, wound dressings, training pants, wipes, mats and the like are known. As a general rule, the absorbent composites comprise an absorbent matrix of fibers. Such a fiber matrix tends to have a relatively low specific absorption capacity. Accordingly, absorbent products needing a relatively high absorbent capacity and employing such a fiber matrix tend to be relatively thick and bulky. In an attempt to increase the absorbent capacity of the fiber matrix, absorbent materials, known in the art as superabsorbents, have been introduced into the fiber matrix. As a general rule, the fiber of the matrix and the absorbent material are intermixed in an air stream and deposited on a porous forming surface to form a relatively lofty mixture of absorbent material and fiber. Such mixtures are known in the art as air-laid, or air-formed structures.
In an attempt to produce thinner absorbent composites and products, more absorbent material has been added to the air-laid fiber matrix. Unfortunately, the porous nature of the air-laid fiber matrix may prevent it from containing relatively high amounts of absorbent material.
As an alternative to air-laid absorbent composites formed from fibers and absorbent material, it has been proposed to form absorbent composites from wet-laid fibrous structures such as tissue, in conjunction with absorbent material. For example, U.S. Pat. No. 3,686,024 issued Aug. 22, 1972, to Nankee et al. describes a process of making a water-absorbent coated article and the resulting product. Described is a fibrous support on which a water-swellable, substantially water-insoluble polymer gel, substantially swollen with water, is impressed.
Similarly, U.S. Pat. No. 4,260,443 issued Apr. 7, 1981, to Lindsay et al. is directed to a laminated absorbent process. Disclosed is a process in which a dry, liquid-absorbing material is applied to a first sheet. A second water-permeable sheet is superimposed on the first sheet. Water is applied at spaced points to the second sheet to moisten the liquid-absorbing material and cause it to serve as an adhesive, bonding the first and second sheets together.
U.S. Pat. No. 4,851,069 issued Jul. 25, 1989, to Packard et al. is directed to a process for making tissue-absorbent particle laminates. According to the described process, a moistening liquid is applied to a first tissue layer. The moistened surface of the first tissue is showered with dry absorbent particles, which particles are of a nature to be rendered adhesive by absorption of the moistening liquid. A second tissue is superposed on the first tissue, and the tissues bonded together by passing through a nip between heated rollers.
European Patent Application 0 359 615 published Mar. 21, 1990, is directed to the manufacture of superabsorbent composite structures. Described is a method wherein a water-laid web of cellulosic fibers is formed. A dry, solid absorbent is applied directly to the web prior to drying of the web and a pre-formed web is laid over the absorbent. The resultant laminated web is then dried.
As a general rule, the products and processes described above involve forming a laminate of an absorbent material with one or two pre-formed layers of fiber material. Such laminated structures have been found to be quite useful. Unfortunately, it is sometimes difficult to effectively contain large quantities of absorbent material between the two layers of fiber material. Additionally, when relatively large quantities of absorbent material are present between the two layers, the laminates tend to delaminate. The problem of delamination is particularly noticed when the laminates are wetted.
As an alternative, U.S. Pat. No. 4,986,882 issued Jan. 22, 1991, to Mackey et al. describes an absorbent paper comprising a polymer-modified fibrous pulp and a wet-laying process for the production thereof. Described are wet-laid paper sheets formed from two or more fibrous cellulosic pulps. One of the pulps is a polymer-modified pulp capable of being protonated and which, in its alkali-metal-cation exchange state, imbibes water by hydrocolloidal swelling. The second pulp is a non-polymer modified cellulosic pulp. The absorbent paper sheet is made such that the first pulp is wet laid in a protonated state such that it tends not to swell. The wet-laid web is then brought to the alkali-metal-cation exchange state and dried.
Those processes involving a substantial pre-swelling of the absorbent material tend to be costly due to the difficulty associated with removing water from such absorbent materials.
It is desired to provide an absorbent composite and a method for making the absorbent composite which are improved when compared to the prior art.